Molecular recognition defines a process of the selective bonding between a receptor (host) and a substrate (guest) to generate a particular function. The concept of molecular recognition originates from the research of interaction relationships between the hosts and guests in the process of life, such as enzyme and substrate, the proteins and nucleic acids, hormones and receptors, antigen and antibody. With the advance of the life science and technology, many enzymes and antibodies extracted from the organism have been used for biological sensing and the resultant biosensors have been applied in the field of clinical testing, pharmaceutical analysis, gene diagnosis, cancer treatment and environmental monitoring. However, there are several significant disadvantages of these biosensors, such as stringent environmental requirements, short shelf life and high production cost. Recently, the molecularly imprinted technology (MIT), developed from the perspective of bionics, combining the advantages of polymer materials science, analytical chemistry, life sciences and bio-engineering, artificially synthesize polymer materials which could exactly match with a particular molecule (imprinted molecules, template molecules) in space and binding sites to realize molecular recognition. The obtained molecularly imprinted polymers (MIPs), so-called “plastic antibodies”, possess more practical value because of the similar recognition properties and selectivity as natural antibodies, as well as the same high stability and environmental tolerance as polymers.
During the procedure of fabricating molecular recognition sensors with the molecular imprinted polymers, the immobilization of imprinted polymers onto the surface of transducer is the key point. Although polymeric film could be formed on the surface of transducer through traditional coating methods, there are several disadvantages of those obtained manual coatings, such as inhomogeneity, uncontrollable coating thickness, and easy desquamation from the surface of transducer. Due to those drawbacks, the molecular recognition sensors prepared by the coating methods have inferior reproducibility and stability, as well as short shelf-life. With the development of polymer synthesis technology, in-situ grafting methods are applied to immobilize imprinted copolymer onto the surface of transducer. A stable covalent binding could be formed between the transducer and the imprinted polymers via this method. The resultant imprinted polymer film is a nanometer ultra-thin film of uniform thickness, possessing good molecular recognition sensing property. However, the controlled radical polymerization reaction (such as ATRP, RAFT) used in the in-situ grafting method needs complex catalytic initiator system and harsh reaction conditions, which greatly retard the wide application of this method. Electrodeposition provides another efficient way to form a film on transducer. Compared with the aforementioned methods, the film formed by electrodeposition is uniform and controllable in thickness. In addition, the electrodeposited films possess excellent adhesion and good weather ability. Currently, the electrodeposition technology, so-called “electrophoresis” in the industry, has been widely used in the coating of the cars and various kinds of metal devices.